1. Field of the Invention
The present invention relates to position sensing technology and more specifically to a variable size sensing system and a method for redefining the size of a sensing area thereof.
2. Description of Related Art
Referring to FIG. 1, a conventional sensing system 100 includes a panel 110, image sensing devices 120 and 130, and a processing circuit 140. The panel 110 includes a touch surface 112, and the shape of the touch surface 112 is a rectangle. The image sensing devices 120 and 130 are located at different corners of the touch surface 112 yet along a same boundary thereof so that the sensing ranges of the image sensing devices 120 and 130 respectively cover the touch surface 112. The image sensing devices 120 and 130 are both connected to the processing circuit 140.
When a pointer 150 touches the touch surface 112 or is placed in the proximity thereof, the image sensing devices 120 and 130 can respectively sense the pointer 150 along the sensing lines 162 and 164. Thus, the processing circuit 140 can identify the sensing lines 162 and 164 from the images that the image sensing devices 120 and 130 sense, and calculate the positional coordinates of the pointer 150 according to the two sensing lines so as to complete sensing the position of the pointer 150.
However, since the image sensing devices 120 and 130 are fixed onto or embedded into the panel 110, the distance between the two image sensing devices is fixed. Once the size of the panel 110 is chosen, the sensing area in which a user can input coordinates is fixed and there is no way to change it.